Vertebral disc herniation or degeneration are a common disorder where a portion of a vertebral disc, a cushion-like structure located between the bones of the spine, bulges out or extrudes beyond the usual margins of the disc and the spine. Disc herniation or degeneration are believed to be the result of a loss of elasticity of the tissue comprising the disc, and is associated with increasing age. Disc herniation or degeneration and other degenerative disc disease are also associated with spinal stenosis, a narrowing of the bony and ligamentous structures of the spine. Although disc herniation or degeneration can occur anywhere along the perimeter of the disc, it occurs more frequently in the posterior and posterior-lateral regions of the disc, where the spinal cord and spinal nerve roots reside. Compression of these neural structures can lead to pain, parasthesias, weakness, urine and fecal incontinence and other neurological symptoms that can substantially impact basic daily activities and quality of life.
Temporary relief of the pain associated with disc herniation or degeneration are often sought through conservative therapy, which includes positional therapy (e.g. sitting or bending forward to reduce pressure on spine), physical therapy, and drug therapy to reduce pain and inflammation. When conservative therapy fails to resolve a patient's symptoms, surgery may be considered to treat the structural source of the symptoms. Surgical treatments for disc herniation or degeneration traditionally involve open procedures that require extensive dissection of muscle, connective tissue and bone along a patient's back to achieve adequate surgical exposure. These surgeries also expose the patient to a significant risk of complications, due to the presence of critical neurovascular structures near the surgical site. For example, a discectomy procedure may be used to decompress the herniation by accessing the affected disc and removing a portion of the disc and any loose disc fragments. To achieve sufficient access to the affected disc, a portion of the lamina or bony arch of the vertebrae may be removed, thereby increasing the invasiveness of the procedure. When discectomy fails to resolve a patient's symptoms, more drastic measures may include disc replacement surgery or vertebral fusion.